Abstract. This study explores a domain-filling trajectory approach to generate a
global ozone climatology from relatively sparse ozonesonde data. Global
ozone soundings comprising 51 898 profiles at 116 stations over 44 yr
(1965–2008) are used, from which forward and backward trajectories are
calculated from meteorological reanalysis data to map ozone measurements to
other locations and so fill in the spatial domain. The resulting global
ozone climatology is archived monthly for five decades from the 1960s to the
2000s on a grid of 5° × 5° × 1 km
(latitude, longitude, and altitude), from the surface to 26 km altitude. It
is also archived yearly for the same period. The climatology is validated at
20 selected ozonesonde stations by comparing the actual ozone sounding
profile with that derived through trajectory mapping of ozone sounding data
from all stations except the one being compared. The two sets of profiles
are in good agreement, both overall with correlation coefficient r = 0.991
and root mean square (RMS) of 224 ppbv and individually with r from 0.975 to
0.998 and RMS from 87 to 482 ppbv. The ozone climatology is also compared
with two sets of satellite data from the Satellite Aerosol and Gas
Experiment (SAGE) and the Optical Spectrography and InfraRed Imager System
(OSIRIS). The ozone climatology compares well with SAGE and OSIRIS data in
both seasonal and zonal means. The mean differences are generally quite
small, with maximum differences of 20% above 15 km. The agreement is
better in the Northern Hemisphere, where there are more ozonesonde stations,
than in the Southern Hemisphere; it is also better in the middle and high
latitudes than in the tropics where reanalysis winds are less accurate. This
ozone climatology captures known features in the stratosphere as well as
seasonal and decadal variations of these features. The climatology
clearly shows the depletion of ozone from the 1970s to the mid 1990s and ozone
increases in the 2000s in the lower stratosphere. When this climatology is
used as the upper boundary condition in an Environment Canada operational
chemical forecast model, the forecast is improved in the vicinity of the
upper troposphere-lower stratosphere (UTLS) region. This ozone climatology
is latitudinally, longitudinally, and vertically resolved and it offers more
complete high latitude coverage as well as a much longer record than current
satellite data. As the climatology depends on neither a priori data nor
photochemical modeling, it provides independent information and insight that
can supplement satellite data and model simulations of stratospheric ozone.